# Candida albicans colonization modulates murine ethanol consumption and behavioral responses through elevation of serum prostaglandin E2 and impact on the striatal dopamine system

## TL;DR

A gut fungus called Candida albicans reduces ethanol consumption in mice by increasing a brain signaling molecule called PGE2, which affects behavior and learning.

## Contribution

This study is the first to show that Candida albicans in the gut can influence ethanol preference and related behaviors through PGE2 signaling.

## Key findings

- Mice colonized with Candida albicans showed reduced ethanol consumption and preference.
- Elevated PGE2 levels in these mice were linked to reduced ethanol preference, which could be reversed with PGE2 receptor antagonists.
- C. albicans colonization altered dopamine receptor transcription and affected ethanol-induced motor coordination impairment.

## Abstract

Candida albicans is a commensal yeast that is a common component of the gastrointestinal (GI) microbiome of humans. C. albicans has been shown to bloom in the GI tract of individuals with alcohol use disorder (AUD) and can promote and increase the severity of alcoholic liver disease. However, the effects of C. albicans blooms on the host in the context of AUD or AUD-related phenotypes, such as ethanol preference, have been unstudied. In this work, we report a reduction in ethanol consumption and preference in mice colonized with C. albicans. C. albicans-colonized mice exhibited elevated levels of serum prostaglandin E2 (PGE2), and the reduced ethanol preference was reversed by injection with antagonists of PGE2 receptors. Furthermore, injection of mice with a PGE2 derivative decreased their ethanol preference. These results show that PGE2 acting on its receptors prostaglandin E receptor 1 (EP1) and prostaglandin E receptor 2 (EP2) drives reduced ethanol preference in C. albicans-colonized mice. We also showed altered transcription of dopamine receptors in the dorsal striatum of C. albicans-colonized mice and more rapid acquisition of ethanol-conditioned taste aversion, suggesting alterations to reinforcement or aversion learning. Finally, C. albicans-colonized mice were more susceptible to ethanol-induced motor coordination impairment, showing significant alterations to the behavioral effects of ethanol. This study identifies a member of the fungal microbiome that alters ethanol preference and demonstrates a role for PGE2 signaling in these phenotypes.

Candida albicans is a commensal yeast that is found in the gut of most individuals. C. albicans has been shown to contribute to alcoholic liver disease. Outside of this, the impact of intestinal fungi on alcohol use disorder (AUD) had been unstudied. As AUD is a complex disorder characterized by high relapse rates and there are only three FDA-approved therapies for the maintenance of abstinence, it is important to study novel AUD contributors to find new therapeutic targets. Here, we show that an intestinal fungus, C. albicans, can alter mammalian ethanol consumption through an immune modulator, prostaglandin E2. The results highlight novel contributors to AUD-related phenotypes and further implicate the gut-brain axis in AUD. Future studies could lead to new therapeutic avenues for the treatment of AUD.